In curing a resinous coating composition applied on electric appliance, electronic parts, automobile, air-craft parts, plant material and the like, has been widely adopted a method wherein a curing agent as amino resins, isocyanate compounds blocked isocyanate compounds and the like is compounded with the abovementioned coating composition and applied composition is cured by effecting a cross-linking reaction, or a method wherein unsaturation bonds are beared on the base resin and a curing reaction is effected through oxidative polymerization. However, these curing reactions always require a high temperature and hence, in the case of curing with an aminoplast resin, there are problems of liberation of volatile materials as alcohol, water and the like or problems of stability of the formed bond after said curing reaction, and in the case of curing with an isocyanate compound, problems of handing difficulties of two liquid packages, application difficulties and the like. Attempts have also been made to use a high solid paint with a resinous material having relatively small molecular weight or a resin having specific polymer structure as comb structure, linear structure, star structure or the like to lower the viscosity of the paint composition.